Portrait photographs are often taken with digital cameras in portrait studios or outside environments. One of the advantages that digital photography has over traditional film-based photography is that digital images can be further processed even after the camera has taken and stored the image. Because the digital image is stored as digital data that fully describes the digital image, digital processing can be used to manipulate that data in a wide variety of ways. Such digital processing includes background replacement technology. Background replacement technology typically operates to remove portions of an image associated with a background behind the subject, and to replace those portions of the image with one or more replacement images.
One example of a background replacement technology involves chroma key technology (also sometimes referred to as blue screen or green screen technology). The chroma key technology is a post-production technique for compositing or layering two images or video streams together based on color hues. There are limitations to chroma key technology, however. For example, it is difficult to accurately distinguish the subject from the background when the subject's clothing is similar in color to the selected background color. Additionally, variations in the background color, such as caused by wrinkles in the background material or shadows cast by the subject, can also make it difficult to properly distinguish the subject from the background.